Field of the Invention
The invention relates to a device for forming an auxiliary sheet pile during a nonstop pile change in a delivery of a printing press, wherein an auxiliary pile carrier for temporarily receiving oncoming sheets is insertable in a sheet feeding direction between two sheets separated from one another at respective trailing edges thereof, and a separator sword briefly supports an upper one of the two sheets at the rear edge thereof over the entire width of the respective sheet, until the auxiliary pile carrier has reached an inserted position thereof.
Such construction features have become known heretofore from the published German Patent Document DE 12 31 721 C1. A lattice or grating mechanically insertable between two successively arriving sheets in the sheet feeding direction forms the auxiliary pile carrier or support in the heretofore known construction, whereon the sheets temporarily form an auxiliary pile, so that the main sheet pile can be removed and a new main sheet pile carrier or support can be brought into position. The pile change takes place while the press is running and during a printing run. At least in presses with relatively high printing speeds, it is necessary to reduce the press speed to change piles, in order to permit the insertion of the lattice or grating between two successively oncoming sheets. The pile changing sequence may occur automatically, if necessary or desirable. Other auxiliary pile carrier constructions which are suitable for mechanical insertion are disclosed, for example, in the published German Patent Documents DE 30 28 865 A1 or DE 42 21 928 A1.
Mechanically displaced auxiliary pile carriers in this or in modified constructions have heretofore not gained acceptance in high-speed presses, especially when thin paper grades are being processed thereby. The insertion and removal of the auxiliary pile carrier with the attendant damage to sheets of paper represent a major problem. Proposals do exist for reducing the friction between the auxiliary pile carrier and the lowermost sheet in the auxiliary pile, such as auxiliary pile carriers with roller elements or with a coating on the surface thereof which reduces friction, however, in high-speed presses and when thin printing stock is to be processed, a breakthrough has proved unachievable, so that the application of such provisions remains limited to printing presses for cardboard or pasteboard and the like.
From the published German Patent Document DE 42 178 16 A1, a device for continuous delivery of segments which have been cut from a web of printing material has become known heretofore, wherein a lowerable or downwardly movable auxiliary pile unit has both a remote-controlled auxiliary pile support, which is extensible horizontally inwardly and outwardly, and a remote-controlled separator belt, for separating the continuously arriving stream of segments in a defined manner into a main pile and an auxiliary pile. Particularly with thin materials, however, the upper segment resting on the separator belt may slip when the auxiliary pile support is inserted and may be damaged at the leading edge thereof.